Massive MIMO Systems with Uniform Planar Arrays: Antenna Selection and Directivity Trade-Off

Uniform planar arrays (UPAs) are widely employed in practical systems, yet the study of antenna selection for UPAs remains limited. In particular, the interplay between selected antenna subsets and directivity has been overlooked in the existing literature. This paper addresses this by exploring how different subsets of selected antennas affect directivity and developing effective antenna selection strategies for UPA with a rectangular lattice. Our findings reveal that different subsets of selected antennas can lead to significantly different values for directivity, influencing selection outcomes compared to scenarios where directivity is not considered. Furthermore, we propose and compare four antenna selection strategies: 1) Column Selection (RS), 2) Row Selection (CS), 3) Full Aperture Greedy Selection (FAGS), and 4) Hybrid Initialization Binary Particle Swarm Optimization (HBPSO). With careful initialization of the particles, HBPSO achieves a spectral efficiency performance close to exhaustive search and surpasses other strategies. Moreover, incorporating directivity into the selection process significantly affects the performance of these strategies.